A cermet alloy is a composite material combining the hardness characteristics of carbide and nitride, etc. with the toughness of metal. Ordinarily, the metal is present in the composite material in the form of a bonding phase and the carbide and nitride, etc., are present as hard particles.
The hard particles include carbides such as TiC (titunium carbide) and WC (tungsten carbide), etc., nitrides such as Si.sub.3 N.sub.4 and TiN, etc., and borides such as TiB.sub.2 and MoB, etc. Cermet alloys of TiC--Ni, TiC--WC--Co, and TiC--WC--Co--Ni in which Ni or Co (Cobalt) bonds these particles, and cermet alloys with this TiC replaced with TiCN, are well known.
In the ordinary case of cermet alloy production, its toughness is reduced when selection of the materials and the blending method are chosen to attain better hardness, but on the contrary, its hardness declines when aiming at better toughness. For example, in the case of the TiC--WC--Co group, if the content of Co is reduced, its hardness is improved while its toughness is adversely affected. Also, when the Co content is reduced, sintering will be difficult making it impossible to achieve the required density. On the contrary, when Co content is increased, its toughness is improved but hardness is declined. Furthermore, it is necessary to use a special sintering process under pressure such as hot pressing and hot isostatic pressing (HIP), etc. to produce a cermet alloy with excellent hardness and toughness, thus making the production process much more complicated.